Gliomas are the most common solid tumors of childhood, with pediatric gliomas among the most recalcitrant. Activation of both mitogen protein kinase (MAPK) and phosphatidylinositol-3' kinase (PI3K) signaling in pediatric low-grade gliomas (PLGG) indicates possible efficacy for agents that target these cascades. This proposal assesses molecular underpinnings of response to promising targeted agents for clinical treatment of PLGGs, and incorporates preclinical testing of novel and translatable combination therapies to (1) define the best therapy for each molecular aberration identified in PLGGs, including BRAF alterations and recently described non-BRAF fusion genes, (2) overcome innate, intrinsic resistance to MAPK/ERK and PI3K/mTOR inhibitors and (3) address acquired resistance in the PLGG setting. We will capitalize on a rapidly accruing multi-institutional phase 2 clinical trial of everolimus for recurrent PLGGs in which acquisition of tissue from all children will allow us to test the hypothesis that PI3K/mTOR activation will predict response to mTOR inhibition. We will further capitalize on our recent success in cloning all PLGG BRAF-fusions characterized to date as well as recently described non-BRAF fusion genes. We hypothesize that each molecular subtype of PLGG will require a distinct and separate targeted approach to maximize efficacy and overcome resistance. Our overall goal is to set the stage for a personalized combinatorial approach for the treatment of PLGGs by generating pre-clinical and clinical data that will determine the best combination of agents for each molecular subtype and enable the next generation of clinical trials in which rational drug combinations are administered to appropriate patients in hypothesis-driven studies.